Shaft furnace



S"Pt- 26 1950 l M. G. H. M. LPERsoNNE 2,523,835

SHAFT FURNACE l Filedpm'as. 194s Patented Sept. 26, 1950 FFICEv SHAFT FURNACE VMaximilien G. H. M. Lepersonne, Maisons-Laffitte, France Application April 25, 1946, Serial No. 664,842 In France May Z2, 1945 6 Claims. l

The present invention relates to transverse circulation shaft furnaces, that is to say furnaces in which thev matters to be treated are, in the course of their downward movement through the shaft, subjected to the action of a stream of hot gases flowing transversely thereto.

It is known that transverse circulation of the heating gases has for its effect to avoid the dependence that exists, in shaft furnaces of the socalled counter-current category, between the value of the section afforded for the passage of the solid material and that of the section afforded for the passage of the gaseous stream.

But, in counterpart to this advantage, transverse circulation involves a specific inability to utilize as fully as with a counter-current circulation, the heat of the gaseous stream and therefore requires a greater volume of heating gases for obtaining the same eifect.

In practice, this specific inability is further accentuated by the fact that the factors of operation of the furnace, to wit the flow rate of the gaseous stream, the length of its travel through the solid mass, the size of the solid fragments and the length of time for which they are heated should be chosen by taking into account certain relations that must exist between them.

If these relations are not complied with, the unitary production capacity of the shaft furnace and the rate of utilization of the heat supplied by the gases are reduced to a degree which may be very important.-

The chief object of the present invention is to eliminate Vthese drawbacks and to improve the furnaces of the kind vin question in such manner as:

1. To increase the rate of utilization of the heat present in the gases and to give this rate a value practically equal to that obtained with countercurrent circulation;

2. To permit of ensuring an accurate adaptation of the proportions to be observed between the various factors to be considered: flow rates of the solid and gaseous streams, length of the gaseous travel, size of the solid fragments, duration of the heating of the solid mass, whatever lbe the capacity of production of the furnace;

3. To increase, to an important degree, the capacity of production per unit of volume of the shaft;

4. To permit the treatment of solid materials reduced into very small fragments.

The principle of my invention consists chiefly in subdividing the shaft into a plurality of superposed sections and causing the stream of hot gases admitted into the lower section, to pass,

after having flown transversely through said section, into the section located immediately` `transverse direction, at higher and higher levels.

Another feature of my invention which is preferably to be utilized'simultaneously with that above-set forth but can be utilized independently, consists in subdividing the shaft vertically into several juxtaposed elements through which distinct streams of hot gases ow transversely, the width of each element and, consequently, the thickness of the layer of solid materials through which the gaseous streams must ow being judiciously determined as a function of the size of the solid fragments that are treated and/or of the gaseous flow rate so that the pressure drop in each gaseous stream remains below a given limit.

lPreferred embodiments of my invention will be hereinafter described with reference to the accompanying drawings, given merely Iby way of example and in which: i

Figs. l and 2 show, in diagrammatic vertical section, two shaft furnaces of the transverse circulation type made according to two different embodiments of the invention, respectively.

In the example shown by Fig. 1, the metallic wall l of the shaftis given the shape of a quad-V rangular vertical prism, of rectangular or squareshaped section, with a feed orifice 2 at the top, and a conical outlet 3 at the bottom. In the furnace is provided a vertical passage 4 limited, across the whole width of the shaft, by two perforated walls or grids 51 and 52, and through which the fragments of matter to be treated move downwardly.

According to my invention, the furnace is divided into several superposed sections for instance two sections which correspond. substantially, but not necessarily, each to one half of the height of the shaft. these two sections is materialized by a constrioted portion or neck 6 pro-vided in passage 4 at this place and by a limitation in the upward direction of the zone of admission of the hot gaseous stream. This stream enters the bottom part of -the shaft through at least one orifice 'l of adjustable section opening into the space between the lateral left wall of shaft l and perforated wall 51. The limitation of the admission zone is ensured by a solid horizontal partition 91 which divides said space into two'chambers S and il The separation betweenl I'he space between perforated partition 52 and the right hand wall of the shaft is divided into two compartments Illa and IIlb by a. partition 92 analogous to 91 and a conduit 20 leads from compartment Iia to interval I I.

The hot gas stream, admitted at 1, therefore passes through the holes of partition 51, ows through the solid matters that are present in the lower half of passage 4, enters compartment Illa, and flows upwardly through this compartment. The gases collected in the upper portion of compartment IIla are led to chamber I I through conduit 20 and flow, in the same transverse direction as the first time, through the upper section of passage 4, into compartment Illb while the outflow of the gases takes place through one or several orifices I2 provided at the top of compartment I 0b.

Owing to the path of travel followed by the stream of hot gases through theshaft, from its inflowv to its outflow, in the course of which said stream is caused to flow twice, in the same transverse direction and in different respective thermic conditions, through the material to be treated, I ensure a heating of this material which isanalogous to the methodical heating obtained in a shaft furnace with counter-current circulation.

This constitutes an important advantage with respect to the kind of heating that takes place in known transverse circulation shaft furnaces. In these furnaces, the heat of the gases is utilized but in an incomplete manner due to the fact that, as the temperature of the solid material rises more and more as the material is moving down through the shaft, said material becomes less and less capable of absorbing the heat supplied by vthe gaseous stream passing transversely through the s-haft with a uniform flow rate over its whole height. It follows that, while the temperature of the gases that leave the furnace is, at the top, little different from the temperature of( the solid materials that have just entered the.- shaft, it rises gradually toward the bottom of the shaft where it becomes equal to the temperature o-f the gases entering the shaft. Consequently, the gaseous s-tream issues from the uppelportion of the shaft at a mean temperature approximating that of the matters that have just entered the furnace and from the lower portion of the shaft at a mean temperature approximating its own inlet temperature. Thus, for instance, if the solid materials and the hot gases are introduced into the shaft at respective temperatures o-f 150 C. and 400 C., the mean temperature of the outowing gases is 230 C.

On the contrary, if, according to the invention, the solid materials and the hot gases are admitted at 2 and at 1 at the same respective temperatures as above stated, the gaseous stream, after owing successively through the lower half and the upper half of the shaft, has a mean temperature of 163 C. at outlet I2. The thermic balance of the furnace has, therefore, been considerably improved owing to a more efficient exploitation of the heat fed by the gaseous stream and to a more rational heating eifect on a solid mass of smaller height and the particular temperature of which is such, when this mass is in contact with the gaseous stream, that it can more easily absorb the heat supplied by this stream.

In the example shown by Fig. 2, shaft I is divided in the transverse direction, into several elements, for instance four in number, respectively designated by A, B, C and D. Elements A and B or C and D are separated from each other by an intermediate wall including a solid middle partition I 3 and two perforated lateral partitions |41 and |42 so as to form passages |61, |62, |63 and It4 through which gaseous streams can circulate.

The distance between a lateral wall of the shaft and an adjacent intermediate wall or between two adjacent intermediate walls, that is to say the width of passages A, B, C, D is judicious- 1y calculated with a view to improving the rate of utilization of the heat of the gases and to permitting the treatment of solid fragments of very reduced dimensions which, up to now, could hardly be treated in furnaces of this kind.

It is known that the coefficient of heat transmission between a gas and a solid is in direct ratio to the iiow rate of the gaseous stream and in inverse ratio to the dimensions of the solid fragments. Therefore, the specific resistance opposed by the solid mass to the circulation of the gaseous stream is proportional to the coefficient of heat transmission. In order to increase this coefficient of transmission without involving an excessive pressure drop in the gaseous stream, the spacing of the vertical partitions and consequently the number of elements of the shaft, are chosen as a function of the gaseous flow rate and of the size of the solid particles treated in the furnace, so thatthe pressure drop in the gaseous stream does not exceed a fixed value.

Owing to the increase of velocity of the gaseous flux, which results from the fact that the gas must flow through a smaller thickness of solid materials, and to the possibility of treatingl materials constituted by finer particles, I obtain an increase of the heat transmision co eiiicient which corresponds to a, considerable improvement of the unitary treatment capacity of the shaft as illustrated by the following example: v

In a given case where the relations to be observed between the various factors above mentioned imposed a height of the shaft equal to ten times its width, it has been possible to reduce its necessary height to 1.25 times this width by subdividing the shaft, in the transverse direction, into four elements and the unitary treatment capacity has been brought to eight times what it was initially.

In the example shown by Fig. 2, I have vused not only the last mentioned feature, but also the feature above described with reference to Fig. 1, according to which the shaft is divided into two distinct sections superpcsed to eachother and through which the same portion of the total gaseous stream flows successively. However, this combination is not necessary in all cases and it may `be sufficient to divide the shaft, over its whole height, into a single series of juxtaposed distinct elements. v

In the example shown by Fig. 2, the gaseous streams are introduced through orifices 11, 12 and 13 into the lower compartments 31, 82 and 83. 'I'hese distinct streams flow separately in the transverse direction through the solid masses present in the passages |51, |52, I53'and I54'of the lower half of the shaft and enter chambers |61, |62, I6,3 and |64. From these chambers, the gases pass,v through conduits 201, 202, 202, 2li4 into chambers I1, I I2, II3 and thence through the solid masses present in the passages |11, |12, I13 and I14 of the upper half of the shaft, toward upper chambers 2|1, 2I2, 2|3 and 2|4 provided with outlet orifices |21, |22, I 23 and |24. It should be noted that compartments 82 and I2 are 5 separated from each other by'an auxiliary partition |85, chamber |81 is separated fromchamber 2 I1 by a partition 81 and so on. f

This transverse circulation shaft furnace complies well with the conditions above set forth and is well adapted'to the thermic treatment of any solid material in fragments or particles of any degree of granulometry, and, in particular, much ner than could be treated up to now in lfurnaces of this kind. Furthermore, the thermic and unitary output of such a furnace are much better due to the rational circulation that is adopted for the gaseous stream with a view to bringing it into contact with the fragmentary or granular material.

It should be well understood that my invention is in no way limited to the embodiments above described, which have been given merely by way of example.

What I claim is:

1. A shaft furnace which comprises, in combination, a vertical shaft, at least two transverse vertical perforated partitions in said shaft extending each from one side thereof to the opposite side so as to form between them a passage for the solid material to be treated, with two distinct chambers left on opposite sides of said passage respectively for the now of the gaseous stream used for heating this material, two partitions transverse to the vertical direction extending each between one of said perforated partitions and the adjacent shaft wall so as to divide each of said chambers into two superposed compartments, the lower compartment of one chamber being provided with a gas inlet, and a conduit outside of said passage, connecting the lower compartment of the other chamber with the upper compartment of the first chamber, the upper compartment of the second mentioned chamber being provided with a gas outlet.

2. A shaft furnace which comprises, in combination, a vertical shaft, at least two transverse vertical perforated partitions in said shaft extending each from one side thereof to the opposite side so as to form between them a passage for the solid material to be treated, with two distinct chambers left on opposite sides of said passage respectively for the ow of the gaseous stream used for heating this material, two partitions transverse to the vertical direction extending each between one of said perforated partitions and the adjacent shaft wall so as to divide each of said chambers into two superposed compartments, the lower compartment of one chamber being provided with a gas inlet, a conduit outside of said passage, connecting the lower compartment of the other chamber with the upper compartment of the first mentioned chamber, the upper compartment of the second mentioned chamber being provided with a gas outlet and means for restricting the horizontal section of said passage substantially at the level of said partitions transverse to the vertical direction.

3. A shaft furnace which comprises, in combination, a vertical shaft, at least two transverse vertical perforated partitions in said shaft eX- tending each from one side thereof to the'opposite side so as to form between them a passage for the solid material to be treated, with two distinct chambers left on opposite sides of said passage respectively for the flow of the gaseous stream used for heating this material, and at least one pair of horizontal partitions extending each between one of said perforated partitions and the adjacent shaft wall so as to divide each of saidl chambers into at least two superposed compartments, the lower compartment of one chamber being provided with a gas inlet, a conduit outside of said passage, connecting the lower compartment of the other chamber with the upper compartment of the first mentioned chamber,

' the upper compartment ofthe second mentioned chamber being provided with a gas outlet.

4. A shaft furnace which comprises, in vcombination, a vertical shaft, at least two transverse vertical perforated partitions in said shaft extending each from one side thereof to the opposite side so as to form between them a passage for the solid material to be treated, with distinct chambers left on either side of said passage for the flow of the gaseous stream used for heating this material, at least one pair of horizontal partitions extending each between one of said perforated partitions and the vadjacent shaft wall so as to divide each of said chambers into at least two superposed compartments, the lower compartment of one chamber being provided with a gas inlet, a conduit outside of said passage, connecting the lower compartment of the other chamber and the upper compartment of the first mentioned chamber, the upper compartment of the second mentioned chamber being provided with a gas outlet, and means for restricting the horizontal section of said passage substantially at the level of said horizontal partitions.

5. A shaft furnace which comprises, in combination, a vertical shaft, at least twotransverse vertical perforated partitions in said shaft extending each from one side thereof to the opposite side so as to form between two such partitions a vertical passage for the downward flow of the solid material to be treated and on either side of this passage a distinct chamber for the upward ow of the gas stream used for heating this material, at least one pair of horizontal partitions in said chambers, respectively, so as to divide each of said chambers into at least two superposed compartments, the lower compartment of one chamber being provided with a gas inlet, and a conduit outside of said vertical passage, yconnecting the lower compartment of the other chamber with the upper compartment of the first mentioned chamber, the upper compartment of the second mentioned chamber being provided with a gas outlet.

6. A shaft furnace which comprises, in combination, a vertical shaft, at least two transverse vertical perforated partitions in said shaft eX- tending each from one side thereof to the opposite side so as to form between two such partitions a vertical passage for the downwardow of the solid material to be treated and on either side of this passage a distinct chamber for the upward flow of the gas stream used for heatingthis material, at least one pair of horizontal partitions in said chambers, respectively, so as to divide each of said chambers into at least twosuperposed compartments, the lower compartment of one chamber being provided with a gas inlet, a conduit outside of said vertical passage, connecting the lower compartment of the other chamber with the upper compartment'of the first mentioned chamber, the upper compartment of the second mentioned chamber being provided with a gas outlet, and means for restricting the horizontal section of said passage substantially at the level of each pair of horizontal partitions.

MAXIMILIEN G. H. M. LEPERsoNNE.

(References on following page) REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,588,217 Winkelman June 8, 1926I 1,692,587 Smith Nov. 20, 1928 8 Number Name Date 1,895,284 Hay Jan. 24, 1933 2,417,393 Evans Mar. 11, 1947 OTHER REFERENCES Modern Furnace Technology, Etherington, Grn & Co., London, 1938, pages 366, 367 and. 368. 

